<ou >o: = CD CO 160315>m OSMAN1A UNIVERSITY LIBRARY Call No. 55 \ "M / ,V^ 6, Accession No. Author P\VVvsMXWv\ j \\ V) 5oV\ Title GvV^Uav VOL^ Q.few^ ^^4 VU This book should be returned on or before the date last marked below. Glacier Variations and Climatic Fluctuations BY H. W:SON AHLMANN SERIES THREE THE AMERICAN GEOGRAPHICAL SOCIETY NEW YORK 1953 BOWMAN MEMORIAL LECTURES Series One. Geography, Justice, and Politics at the Paris Conference of 1919. By Charles Seymour. 1951 Series Two. Agricultural Origins and Dispersals. By Carl O. Sauer. 1952 Copyright, 1953 by the American Geographical Society George Grady Press, New York Foreword THE THIRD in the series of the Isaiah Bowman Memorial Fund lectures was delivered by His Excellency Hans W:son Ahlmann on August 13, 1952, as the principal ad- dress at the meeting of the Seventeenth International Geo- graphical Congress in Washington, D. C. The original text of "Glacier Variations and Climatic Fluctuations" has been augmented for publication by additional data and references to serve as a summary of the author's latest thinking on the subject. It brings together the findings of the human and physical geographer, the geomorphol- ogist, the climatologist and even the historian. Dr. Ahl- mann has been Professor of Geography at the University of Stockholm, and from 1948 to 1951 served as President of the Commission on Snow and Ice of the International Association of Hydrology (I.U.G.G.). Dr. Ahlmann, now serving his country as Sweden's Ambassador to Norway, has for two decades been the leader in the work of relating changes in glaciers to climatic fluctuations. His concept of the need for collabo- ration between sciences the team approach and the ne- cessity for initiating detailed observations to achieve a better understanding of glacier regimen has changed the whole scope of glaciology. He has pioneered in developing methods for making precise measurements of accumula- tion and wastage from which to determine a glacier's econ- omy or hydrologic balance. These techniques not only provide means of learning more about glaciers themselves, but also make possible a much more accurate and satis- factory interpretation of their response to meteorological factors and other external influences. Dr. Ahlmann's studies began in Norway in 1918, were extended to Spitsbergen in 1931, to Iceland in 1936, and to northeast Greenland in 1939. The Norwegian-British- Swedish Antarctic Expedition, 1949-1952, was largely a product of his planning and organization. In the summer of 1952, following the meeting in Washington, he made a brief visit to Southeastern Alaska under the auspices of the American Geographical Society, supported by funds generously provided by the Office of Naval Research. His objective was to observe the principal glaciological fea- tures of that area and to evaluate the studies being made there by this Society and others, in order to further the development of a well-integrated international program of glaciological-climatological research. We may appropriately recall the Foreword he wrote in the first issue of the Journal of Glaciology, January, 1947 (p. 3): "As a science glaciology is young, even though snow, ice and glaciers have been noticed for centuries . . . but they have been remarkably late in becoming the subject of systematic investigation. And this in spite of the fact that snow and ice are of great practical importance in northern countries. . . . We are as yet only on the threshold of the world of ice in the Antarctic that conceals the answer to questions of the greatest importance to the understanding of physical-geographical conditions both at the present time and during the Ice Age. The glaciers at all latitudes round the earth are of no less interest. As yet we know very little about the meteorological reasons for their existence and variations in size, about their structure, movement and [iv] other features. . . . The tasks confronting us are immense and various ..." In this volume, as in his many other writ- ings, Dr. Ahlmann clearly points the way to the future development of glaciology in both its practical and theo- retical aspects, especially as it may contribute to the study of climatic change. W. O. FIELD, JR. [v] Glacier Variations and Climatic Fluctuations I REGARD it as a very great honor to have been asked to give this lecture in memory of Isaiah Bowman, a man whose attainments as a scientist I have long appreciated through his writings and whom I had the pleasure to know personally, not only as a man of great distinction and a citizen of the United States, but as a citizen of the world. As the subject of my lecture I have selected a chapter in climatology. This science is of importance not only to glaciologists; it affects the whole social and economic life of mankind. Isaiah Bowman was much interested in climate and its changes. In studies of the pioneering process, for instance, he gave full recognition to climate as a critical element. He often cited the early Norse settlement of Greenland as an experiment on the "verge of the possible/' where even a slight climatic change brought disaster. 1 And he stressed the need of quantitative study. He himself "car- ried out measurements on physical indications of climatic change on tree rings and on strandlines in Great Basin lakes and later he prompted the National Academy of Sciences to undertake cyclic-change studies in weather and climate." 2 Glaciers and glaciation were a subject of special attention in his field work in the Peruvian Andes. Of recent years, glaciers have been the object of intense scientific research. That research, moreover, is differenti- ated by today's cooperation between various scientific dis- ciplines whereby many new aspects of a more profound geophysical nature have been opened up. To take one ex- ample, it is only within the last 20 years that any close attention has been given to the glacier ice itself. 3 The earlier unconcern has run through the whole course of polar exploration; it applies particularly to Antarctica, with 99 per cent of its area ice covered. Today we have a better appreciation of the necessity for more intimate knowledge of present-day glaciers if we are ever to understand Pleistocene glaciation. Richard Foster Flint's "Glacial Geology and the Pleistocene Epoch/' pub- lished in 1947, is one of the first comprehensive works to use glaciology as a basis for study of this period. His ap- proach became feasible only as a result of the recent rapid advance in glacier study. Our extraordinary technical progress has made it pos- sible to achieve results in practically all branches of science that no one would have dreamed of only a few decades ago. Such, for instance, in the field of polar research, is the determination by the seismic reflection method of the depths of the inland ice plateaus of Greenland and Ant- arctica. In Greenland this has been carried out by the French Polar Missions of Paul-Emile Victor, 4 and in the Antarctic by the Norwegian-British-Swedish Expedition to Queen Maud Land, 1 949- 195 2. 5 SOME PRELIMINARY GLACIOLOGICAL RESULTS FROM QUEEN MAUD LAND Figure i, reproduced with the permission of Gordon Robin of the Queen Maud Land expedition, gives the re- sult of his seismic depth measurements from 71 S. to 74  30' S. It reveals a wild alpine topography covered with ice to a depth of up to 2500 meters an immense mass. On the basis of the French results in Greenland, Andre Cailleux 6 is quite right in saying that previous estimates of the world's existing glacier ice are too small. He calculates that the total volume of land ice must be between 26 and 36 million cubic kilometers. Melting of this volume of ice would raise the sea level by some 65 to 90 meters. Even after making allowance for isostatic adjustments, the rise would be from 43 to 60 meters. Now, as a result of the work in the Antarctic, we can say that the higher figure, 60 meters, is probably a minimum value. I should like to mention here some other results of general interest from the Queen Maud Land expedition. V. Schytt's measurements at Maudheim show that temper- atures in the inland ice and in the shelf ice below the level to which the seasonal fluctuations penetrate (below about 20 meters) correspond to the local mean air temperatures. Thus we have a method of determining this very important climatological element in a given place on the ice, even though we can only stay there for a day or two. Near the southern end of the profile in Figure i, at 2700 meters above sea level, the average temperature for the year has been calculated in this manner to be about -40 C. Temp- eratures below -50 C. must be common in the winter months. The possibility of traveling over the Antarctic and the Greenland icecaps with mechanical snow vehicles may soon bring us to the day when we shall know the average air temperature over the inner parts of these regions. Aside from the value of such information to regional geography, we can reasonably expect that the results obtained may  mw. <U CJ !H 3 .2 S - ""* fepO Ifjj ! 8 'VJ^ \ a* -0 ~ $& cj G bo ~ *rt ^ 1 5 * <$ S ^ *_4 w p r I U-l "^ ^ dj rt w r- ^.s^ O>73 ?^ l. - T3 ' H) in ^ x X;W ' JJ-3 ^ <u C/3 X5 gj-i IS ( oJ ( X S * q serve as a basis for increased knowledge of the climate on and around the masses of Pleistocene inland icein other words, of the climate during the Ice Age. Present-day knowledge about the great ice sheets of the past is ex- tremely limited. I am still convinced that at least most parts of the Pleistocene ice sheets were of polar and not of temperate type, that is to say their temperatures were be- low the freezing point to a depth of at least a couple of hundred meters, with the upper score or more consisting of frozen snow, firn, not ice. 7 Schytt's geophysical and crys- tallographic analysis of a loo-meter-long core at Maud- heim has shown that there was no real glacier ice at lesser depths than Go meters. FACTORS INFLUENCING GLACIER VARIATIONS Glaciers, being conditioned by climatological factors, register by their variations fluctuations and changes of cli- mate. Even the present climates of the world are not stable as was once believed by meteorologists, among them the great Hann. They are, and always have been, subject to fluctuations and changes over both long and short periods. The scope of this field of research is so vast that I must limit myself to the Scandinavian countries and Iceland, with some comparisons from North America. The relations between glaciers and climate are highly complicated and still far from clear. Until we have solved the problems of the existence and the variation in size of glaciers, their structure, movement, and other features, we cannot fully utilize them as the climatological registers they really are. Robert Sharp 8 correctly says that accumula- tion is the life blood of a glacier and that "its state of health  0> 1 s 1 . 1 . .s ti s> G O^ IX) C C/3 S s; s ^ ^ > CO OO XC OO xO Of OO ^^ " oo oo m oo oo S^ CJ j* a XT5 s ^1 3 *> 1 Ci O ^f 1 oo 'c O O Of ' - 04 ' .5 **5 U K f $ a rrH ^3 K o o a> 0) -o > O XO G OO O"> ^* 04 G xO *-* vJ o rf <O 8 oo 04 Tj- o 8 ^ So " U "o .S c 5 1? *o | B 6 S S B B B s ^ o* S S 8 8 8 ^^ J 00 ~ ^ o o o o ^H M P^ <JO Cj 5-H 3 K^ .2 r-2 P* > C ^jj |D ^ W ^> !> ^ W ^ tt} *"* CTJ .s s QJ S rt *8> w O O O xO 2 ^ <o o o o o 1 2 2 O 00 T5 O Of PH P4 PH ? ^ ? ? a, ^ c S O U "ai oo V "b . o "b *-j 'S o o Of O* OO O <-H ^ o o o o o o O"> O"> t"* tO to Tj^ ? U 0? G *? SH (H < c *g 03 <+* ** O g O S3 C "" K^ o ^ "3 H-> 'S 3 M 3 *0 -o 4> cd (-^ 43 C P 5 "* o *^3 # 3 T3 c3 G ^ 5- JH ^ rj _- CTJ 1 5T ^ CH Q^ U W QJ 3 M *U *D 00 '0 00 ^4 ^ ^ s . 03 a oo 5 C *\u Ii vU u ^! o 3* c/i CO pr . OO _CJ CT) CT) t3 - <U - 03 pQ ^~^ c/i r . >-s ~ '^ *C3 ooj O QJ "**** ^st * g s :r 3 X ^ & can best be defined in terms of the relation between accu- mulation and wastage." Ablation, or wasting (melting and evaporation), is the crux of the matter. It seems as if abla- tion is at least as important as accumulation in this appar- ently simple relation. But it is only recently that attention has been turned to the question of which meteorological factors determine ablation in different regions. The basic work in this subject was carried out in 1934 by H. U. Sverdrup on Isachsen's Plateau, a vast snow- covered transection glacier in Spitsbergen. 9 It was con- tinued on the Karsa Glacier, a small cirque or valley glacier in Swedish Lapland, by C. C. Wallen in 1942-1 948. 10 From Wallen's recent review of the most conclusive results," the following can be summarized. The relative importance of the climatic elements determining the "health of the gla- cier" varies from one region to another. As a rule we have to take into account: ( i ) the amount of the annual precipi- tation in solid form; (2) the temperature during that period of the year when it is above the melting point; (3) the length of that period; (4) the amount of incoming and outgoing radiation, both being influenced by the degree of cloudiness; (5) the wind velocity; (6) the humidity. The relative importance of the different factors gradu- ally changes from the beginning of the ablation season to its end. The influence of radiation diminishes from early July onwards. Its effect also depends on the nature of the surface, whether snow or ice, for ice has a smaller albedo than snow. In spite of differences in latitude and local conditions, the most important factors in the ablation process are shown to be convection (heat received from the air) and radiation. Condensation plays a much smaller part, evapo-  ration a still lesser. It seems that the importance of radia- tion increases with decreasing latitude. Table I is repro- duced from Wallen's report. The more maritime and humid the climate the more important in the process is convection. Vatnajokull in Ice- land is a good example of a glacier where ablation takes place under these conditions and where convection plays a much more important part than radiation. 12 On the other hand, in Peary Land in northernmost Greenland, where the climate is extremely continental and arid, evaporation from the icecap is the most important factor in the ablation process. 13 Our present knowledge of glacier variations is mainly based on observations of their size and especially of their marginal variation. But the variations are primarily a con- sequence of the thickening and thinning of glaciers, in other words, of changes in volume. These latter changes are far more difficult and trouble- some to determine than the oscillations of the termini. Here an important question is: When does a glacier front react and, by advancing or retreating, affect its "health"? A small glacier will naturally react sooner than a large one. The rate of reaction is dependent also on the topography. If the gradient is steep or the depth great the glacier will move rapidly and the changes will be transmitted to the terminus more quickly than if the slope is gentle or the thickness small. Advances and retreats will therefore usually begin and end at different times, even in the same region. There is also a difference between glaciers termina- ting on land and in water, especially if the glacier tongue is afloat. The importance of calving is to be considered and the fact that the rate of movement of the glacier increases towards the ice cliff. 14  In the polar regions we must distinguish between the main inland ice masses on the one hand and on the other their outlet glaciers and local glaciers of different types. Because of the very great area of the inland ice in the Antarctic and in Greenland it is difficult to obtain measure- ments that are either representative or accurate enough to lead to any certain conclusion about the ice regime; that is to say, whether the total volume is increasing or decreas- ing. The Antarctic inland ice is largely surrounded by floating shelf ice, the extension of which is dependent on other factors than those of climate and glacial regime alone. In relation to the whole Antarctic inland ice and the main body of the Greenland inland ice, we must also bear in mind that the reaction to changes of climate is very slow. The Antarctic "cold center" especially offers strong re- sistance to external forces. In both these parts of the world the summer temperature is so low that a rise of a few de- grees may not bring the temperature above the melting point, and thus affect the ablation. Variations in the posi- tions of the termini of outlet glaciers from inland-ice masses are related to the supply of ice as it was determined by climatic conditions of a long time before. In a short preliminary review of the scientific work of the Norwegian-British-Swedish Expedition, E. F. Roots 15 points out that "the lag between climatic change and change in form of the glacier may be longer than the period of climatic change itself " and that the Antarctic icecap is one great accumulation area. He adds: "A further possi- bility is that the thickness of the Antarctic ice-cap is not dependent on climatic conditions at all, provided there is sufficient snow accumulation to develop an equilibrium cross-section determined by the physical properties of ice and the resistance offered by the rock floor."  In recent years we have gained knowledge of some special types of high-polar glaciers. The icecaps in Peary Land, where evaporation is predominant among the causes of ablation, are characterized by Fristrup as masses of dead ice, which have possibly grown up under conditions of much greater annual accumulation and surplus in the regime than is the case under present conditions. The outlet glaciers of the inland ice are of a different type; they move fast and transport large quantities of ice. Glacier caps very similar to those found in the interior of Peary Land occur on Baffin, Bylot, and Devon Islands, and the south- ern part of Ellesmere Island. They have been described by Baird, 16 and are classified by him as the "Baffin Type/' Their nourishment is not by accumulation of firn but by superimposed ice from the immediate refreezing of sum- mer melt water. Baird has the same impression as Fristrup, namely that these glacier caps are relics from a climatic epoch of the past, one that was neither so cold nor so arid as the present. The following statement by F. E. Matthes 17 on the laws of ice flow is further of great importance: "Ice confined in a reservoir remains inert under steadily increasing pressure until a certain point is reached when flow sets in slowly at first, but increasing rapidly in velocity, even though the pressure remains constant or is diminished. The flow then continues with gradually diminishing velocity until the reservoir is well depleted, when the ice-mass returns to its inert state. The annual overflow from a glacier cirque does not correspond to the annual accretions; but the snow keeps on accumulating for several years as a rule, until sufficient pressure is reached to inaugurate a strong and rapidly accelerated forward movement. A conspicuous  advance of the glacier front results, which does not stop until the cirque is drained to a lower level/* In a lecture to the Norwegian Polar Club, Oslo, early in 1952, O. Liestol expressed the same opinion. Glaciers have a tendency to establish time variations of their own that are more or less independent of climatic factors. Over a long period of time a surplus may be built up in the accumulation area, while the lower part of the glacier con- currently wastes away until the frictional limit is exceeded, and the ice slides forward. Such a condition, he says, is most evident in polar and subpolar glaciers and, it may also be added, is especially applicable to glaciers whose ac- cumulation areas are situated on plateaus high above the valleys constituting their main ablation areas. Such are the Spitsbergen glaciers, which, moreover, mostly terminate in floating tongues in fiords. For the great majority of glaciers there is obviously a greater or lesser time lag between the beginning of a clima- tic fluctuation and the ensuing marginal variations. Hence it is very unlikely that variations in length of a glacier are strictly comparable with short climatic fluctuations, as, for example, an ii-year sun-spot period. The reactions of different glaciers to climatic fluctuations extending over considerable periods several decades or centuries may, on the other hand, reach their climax at about the same time, provided that the physical structures and morpholo- gy of the glaciers are not too different. GLACIER REGIME IN SWEDISH LAPLAND, 1941-1952 For diagnosis of the "health of a glacier" Wallen from 1941 to 1948 carried out systematic studies on the small Karsa Glacier (2 sq. km.; see PL I A). Since 1946 similar but more detailed investigations have been carried out by Schytt and Woxnerud on the Stor Glacier (3.3 sq. km.; see PL IB) on the highest mountain range of Sweden, Kebnek- TABLE II REGIME OF THE KARSA AND STOR GLACIERS Kdrsa Glacier (68 zo'N., 18 2o'E.; alt. 820-1440 m.) Budget Years Accumulation Ablation Def. ( ) or Def. or Sur. Sur. ( + ) per km. 2 Alt. of Retreat Firn Line of Front Million cubic meters of water Meters Meters (1941-42 1942-43 2-3 3-7 3.8 4.0 1.5 0.8 -0.3 -0.15 135) \ 1150 J 6. 5 1943-44 3-9 3-9 o.o o.o 1 1OO 3.0 1945-46 3-5 4-3 0.8 0.4 1250 1O.O 1947-48 3.6 3-2 +0.4 +0.2 1050 6.0 1948-49 - - - - 4.0 1949-5 - > 5.0 Total 17.0 Mean 1942-43 101947-48 3>/ 19.2 2.2 3.9 -0.2 -i-35 0.1 1150 34-5 Stor Glacier (6y^o'N. f i8^o'E.; alt. 1080-1700 m.) 1945-4 6 3-5 5-5 2.O -0.6 1480 15 1946-47 3-2 9.6 -6.4 -i-9 1600 20 1947-48 4-5 4-5 0.0 o.o 1450 22 1948-49 6.9 4.1 + 2.8 +0.8 1410 H 1949-5 4.4 8.4 -4.0 1.2 155 !9 i95-5i 2-5 4-5 2.0 -0.6 1500 15 1951-52 ca. 2.7 ca. 3.2 ca. 0.5 -0.15 1460 15 1952-53 4-5 Total 27.7 39-8 12.1 -3.6 120 Mean 4.0 5-7 ~i-7 -0.5 1493 17  ajse. 18 The glacier regime, or material balance, is deter- mined for each "budget" year. A budget year begins in the autumn, when the accumulation first exceeds ablation at the firn limit; it thus extends from the first snow fall of winter through the ablation season of the following summer. 19 By regime is meant the total accumulation vol- ume through one accumulation season minus the net ablation during the following melting season, expressed in terms of water. Preliminary results from the Lapland projects are shown in Table II. The values for the Stor Glacier are based on about 10,000 measurements. Total accumulation and ablation have varied consider- ably from one year to another. On the Karsa Glacier the balance between them was negative three years, positive one year (1947-48), and balanced in one (1943-44). The sum total for the five budget years shows a net deficit of 2.2 million cubic meters of water, or o.i million a square kilometer a year. The corresponding figures for the Stor Glacier were five years with negative regime, one with positive and one with balanced; the total deficit for these seven years was 12.1 million cubic meters or 0.5 a square kilometer a year. The retreat of the termini of both glaciers was con- tinuous and proportional to the regime. The regime of the Stor Glacier, it may be added, is representative of the 16 small glaciers lying in the same massif. The highest peak of the Kebnekajse Range is covered by a small glacier that accurate measurement 20 has shown to vary in height with the regime of the Stor Glacier. In 1950 this highest point in Sweden was 2117 meters above sea level. It is important to note that the significance of the air temperature to the glacier regime is determined in par- ticular by its variations around freezing point. It makes no appreciable difference to the majority of temperate glaciers if the winter is more or less cold, whereas the amount of melting during the ablation season is of the utmost con- sequence. High spring and autumn temperatures prolong the ablation period, high summer temperatures intensify it. The negative regime, the thinning, and the retreat of the Stor Glacier during the seven years in which it has hitherto been observed, is a continuation of its behavior during the preceding decades. Since 1908 it has been characterized by recession; concurrently there has been a rise in the spring, summer, and especially autumn tem- peratures in Lapland. THE RECENT GLACIER RECESSION Most glaciers in both northern and southern hemis- pheres are known to have been receding more or less rapidly for several decades. This, "the recent glacier re- cession/' is exemplified by the curves (Fig. 2) showing the variations of glacier termini in some of the best known areas: Scandinavia, 21 Iceland, 22 the Alps, 23 and parts of North America. 24 Large glaciers have become smaller (PL II), small ones have disappeared completely or have be- come dead ice. I will mention some few examples from the Arctic. Most of the outlet glaciers of the Greenland inland ice have been in recession for several decades. 25 Froya Glacier (74 24' N., 20 50' W.) on Clavering Island in northeast Green- land, a local glacier with well-defined boundaries, was in- E JOOO 1000 200 100 100 200 SWEDEN 63N.-68N, Maximum extension end of 17th Century Maximum extension about 1910 (E. Bergstrom) 1675 1700 1725 1750 1775 1800 1825 1850 1875 1900 1925 1950 B 100 200 : 300 STOR GLACIER Swedish Lapland 1725 1750 1775 1800 1825 1850 1875 1900 1925 1950 +1000 0- -1000- -2000- '' f SOUTH NORWAY NIGARDSBREEN, (0. Liestol) 1725 1750 1775 1800 1825 1850 1875 1WO 1925 1950 1000 2000 3000 +2000 D 2+1000- | 0- -1000- +250 -250 -500- -750- -1000 ICELAND, DRANGAJOKULL, 66N. (S. Thorarinsson) ICELAND, VATNAJOKULL, 64N, (S. Thorarinsson) 1750/51 1800/01 1850/51 1900/01 1950/51 SAVOIE, THE ALPS, 45N. (M. Mougin, 0. Liestol) 1600 1625 1650 1675 1700 1725 1750 1775 1800 1825 1850 1875 1900 1925 1950 ilao- x c\ T ^ BRITISH COLUMBI A, 50N. ' ^ (Mt. Garibaldi area, W. H. Mathews) S. E. ALASKA, 60N. (D.B. Lawrence) 1700 1725 1750 1775 1800 1825 1850 1875 1900 1925 1950 FIG. 2 Curves showing the variations of glacier termini. For details on construction of the curves see footnotes 21, 22, 23, and 24. vestigated in 1939-1940, the position of the snout was measured again in 1947 and in 1952. 26 It has continuously receded in a manner which may be said to be representa- tive of the recent glacier behavior in that part of the Arctic. Meters 590 FROYA GLACIER '; ' " +385 *s^_- ^;;c^^, Terminal moraine ---- Glacier Terminus 1939 ^^J Glacier Terminus 1952 150+ Meters above sea level \\ FIG. 3 The snout of Froya Glacier, Northeast Greenland (74 24'N.), in 1952. with terminal moraines indicating its maximum extension, probably in about 1750. The dashed line is the terminus in 1939. On the basis of sketch maps and photographs taken in these years Swithinbank concludes that the snout had receded 75 meters between 1939 and 1947 and a further 50 meters up to 1952 (Fig. 3); this retreat, however, represented a decrease of only about 2 per cent in the total area of the glacier. There was a corresponding thinning of the ice even at altitudes well above that of the snout; for instance, at 450 meters above sea level the glacier surface in 1952 was about 15 meters lower than in 1939. The active bulging tongue that formed the snout when the older photographs were taken had completely disappeared by 1952, leaving only a smooth, partly moraine-covered front of a type more characteristic of a dead ice mass. The Chr. Erichsen Glacier, a special high-polar type in Peary Land investigated by the Danish Expedition, 1947- 1 950, and described by Fristrup, had a negative regime and was receding. A great part of the tableland around the glacier gives the impression of having been only recently laid bare. The Barnes Ice Cap on Baffin Island 27 showed a small deficit for the budget year 1949-1950, that year not being greatly different from the normal during the previ- ous decade. Photographs taken in 1934 and in 1950 show only a barely perceptible thinning in its lower section. It has already been mentioned that in Spitsbergen con- ditions are in many respects peculiar. A summary prepared for me by Liestol, points out that glacier snouts that have receded over a hundred years or so, suddenly begin a rapid advance, sometimes reaching as far as the outermost recent terminal moraines. Every glacier has its own period of variation, which is, however, dependent on the more pro- nounced climatic fluctuations and changes. Measurement of the position of the glacier terminus alone cannot give satisfactory knowledge of the relation between its varia- tions and the climate. It is necessary to investigate the whole glacier. The Finsterwalder Glacier in Van Keulen Fiord, Bell Sound, West Spitsbergen, has recently been the subject of comprehensive studies of the kind needed. In the district south of Bell Sound the total volume of ice in the glaciers was more or less unchanged from 1920 to 1936. The Finsterwalder Glacier itself decreased in vol- ume between 1936 and 1950 and showed a strong negative budget in 1950-1952, mainly because of exceptionally scanty accumulation. Thorarinsson's map (Fig. 4) of two glaciers in southern Iceland, Breidamerkurjokull and Hrutarjokull, supple- ments the curve showing the oscillations of Icelandic glaciers (Fig. zD). The present position of the termini should be about the same as it was in the last part of the FIG. 4 The termini of Breidarmerkurjokull and Hrutarjokull in southern Iceland. The glacier front in 1904 (continuous line) is according to the Danish General Staff; position in about 1850-1890 (dotted line) is based upon the terminal moraines; position in 1950 (dashed line) is according to a survey by the Durham University Iceland Expedition. i7th century; they are much more advanced than in the time of the Sagas (A.D. 870- 1 2 64) , 28 Before turning to North America the recent general re- cession of European glaciers may be noted in summary. A list of measured glaciers for 1 947-5 o 29 shows the following per cent in retreat in 1947-1948: French, 100; Swiss, 77; Italian, 98; Austrian, 89; Swedish and Norwegian, 97; Ice- landic, 88. In total, of 262 measured glaciers 88 per cent were in retreat, only 6.5 per cent advancing. For 1949- 1950 the figures are: French, 93; Swiss, 99; Italian, 96; Austrian, 100; Swedish and Norwegian, 91; Icelandic, 67. In total, of 318 measured glaciers, 96 per cent were in re- treat, 3.5 per cent advancing, 0.5 stationary. Our knowledge of the oscillations of the North Ameri- can glaciers 30 rests partly on old descriptions and photo- graphs and on tree-ring studies and partly on systematic measurements. Conditions in different regions sometimes differ greatly because of morphological and other causes, as I have already mentioned. Moreover a large number of glaciers in Alaska end in fiords and are thus in the same class as the Spitsbergen glaciers with their anomalous variations. Reference should be made here to two important sys- tematic investigations the Arctic Institute of North America's project "Snow Cornice," located on the Seward- Malaspina Glacier System on both sides of the interna- tional boundary line in the St. Elias Mountains, and the Juneau Ice Field Research Project of the American Geo- graphical Society, supported by the Office of Naval Re- search. Both have as a common object to help in putting American glaciology on a dynamic and qualitative base. On the general situation D. B. Lawrence has this to say: 31 "The glaciers emanating from the southern part of the Juneau Ice Field . . . seem to have advanced in unison to a maximum some time in the early or middle eighteenth century, which surely had not been exceeded since before the 1 300% and from which recessions of 1.3 to 5 miles be- ginning by 1765 at the latest subsequently occurred. The  same chronology has been reported from Glacier Bay, Alaska, from Garibaldi Park, British Columbia, from Mt. Hood, Oregon, and even from Norway and Iceland/' In Alaska the behavior of the glaciers has been more heterogeneous than in most other parts of the world. 32 As Matthes earlier pointed out "in a region of such marked topographical diversity as Alaska, it is to be expected that some glacier basins will respond more quickly than others, and on a different scale, to a given change in climatic con- ditions/' Concerning the immense recession in Glacier Bay over 60 miles since the i8th century, of which 16 have been since 1892 I am of the opinion that the most noteworthy fact is the advance of the glaciers in the eight- eenth century rather than the recession which followed. The climate in the lower parts of Glacier Bay district, where the ice has thinned out and from which it has re- treated, is not suited to the survival of great ice masses. Even during a climate more favorable to glaciers than that of the present time, ice transported to the lower parts of the region must melt away more or less rapidly. The prob- lem to be solved is the reason for the catastrophic advance of the glaciers which covered these areas with such a thick sheet of ice. The recession in Glacier Bay cannot be taken as evidence of the importance of the present climatic fluctuation. On the other hand, the glacier advance in the eighteenth century points towards the probability of there having been a climate favorable for glaciers during the preceding centuries. The present advance of Taku, while all other outlet glaciers of the Juneau Ice Field are reced- ing, has attracted attention. Perhaps Matthes' claim of "an upward shift of the zone of maximum snowfall" has actu- ally taken place in some sections of Alaska. 33  A summary, prepared for me by William O. Field, Jr. in the spring of 1 952, gives glacier variations in recent years in that part of North America lying south of Alaska. It makes clear that the rate of recession of several glaciers has decreased appreciably, or has even changed to an advance paralleled by a thickening of the ice. The turning point in some cases occurred about 1945.^ The renewed activity of these glaciers has been intensified rather than dimi- nished during the last two seasons (1951 and 1 952) in spite of their exceptional melting. The behavior of Nisqually Glacier and the other glaciers of the same type is dependent on the relation between snow and ice sources in their upper parts and the melting of their lower parts. 35 Even if the times of maximum glacier extension in dif- ferent parts of the world have differed slightly, there is a striking resemblance in the general trend of variations in Europe and North America. Comparing the results of budget studies in Lapland and Alaska we find a close paral- lel in glacier behavior and temperature development. The 19481949 budget year, which had a strongly positive regime, was clearly marked in both. The size and com- position of the accumulation area on the Seward Glacier also gives evidence of a close parallel in other years. And though the data from other parts of the world is less complete, there are nevertheless signs that the margin- al variations of glaciers have been more or less concurrent in recent centuries all over the world. 36 The ice fields on the large extinct volcanoes of Central Africa have dimin- ished greatly. 37 Old terminal moraines in front of the present glaciers show that they have been much larger in relatively recent times. From the post-glacial maximum extension their retreat appears to have been interrupted  by periods of stagnation and advance. The recession of some was greater after 1 930 than it was in the period 1 900- 1930. At present, however, the Ruwenzori glaciers seem to be in a rather stable condition; accumulation normally ex- ceeds ablation, keeping them well nourished. More or less definite glacier retreats have been reported from Asia Minor, 38 South America (especially Chile 39 ), and also from New Zealand. 40 From the Antarctic we have Schytt's observations from Queen Maud Land in 1950- 1951. They indicate that at present a state of equilibrium exists between nourishment and outflow of the inland ice, and that the ice cover has not thinned during the last decades. THE PRESENT CLIMATIC FLUCTUATION As to the present climatic fluctuation, I should like first to refer to some comprehensive studies, in particular to Leo Lysgaard's "Recent Climatic Fluctuations*' and H. C. Willett's "Temperature Trends of the Past Century." 41 The numerical values on Figure 5 are in tenths of a degree Fahrenheit for the last 20 years, winter temperature change centered to 1930. It is of particular interest to note that the temperature rise has been most pronounced in the northern hemisphere, where it increased with the latitude, the rise reaching its maximum values in Spits- bergen (Fig. 6) and in Greenland. No counterpart is in- dicated in the higher latitudes of the southern hemisphere. We must remember, however, how scattered and tempo- rary the observations have been and still are in the Ant- arctic. Speaking generally, the difference between the sum- 4!? FIG. 5 Twenty-year changes of the mean winter temperatures centered on 1930. The numeric values in tenths of a F. (After H. C. Willett, see footnote 41). C +6 -1-5 - +4 - +3 +2 - +1 - o- -1 - -2 -3- -4 - -5 W. SPITSBERGEN Overlapping 10 years anomalies from mean value 1901-1930 Winter Spring Summer Autumn 1894- -1903 1904- -1913 1914- 1923 1924- 1933 Fir,. 6 Seasonal mean temperatures in West Spitsbergen (78 N.). Overlap- ping lo-year anomalies from the mean value 1901-30.  +19.0 +18.0 +17.0 +16.0 +15.0- 8.0 7 JO 6.0 5.0 4.0 3.0 2.0 0.0- -1.0- -2.0- -3.0- -4.0- -5.0 STOCKHOLM July October April January +18.0 +17.0- +16.0- +15.0- +9.0- +8.0- -J-7.0 +6.0- +5.0- + 4.0 +1.0- 0.0 -1.0 LUND July October April January +i5.a +14.0- +13.0- +12.0- +11.0- -1.0 -2.0- -3.0- -4.0- -5.0- -11.0- -12.0- -13.0- -14.0- -15.0- -16.0 July KARESUANDO October April January FIG. 7 Seasonal temperatures at Swedish stations plotted in lo-year overlapping means: Stockholm (59 so'N.); Lund (55 4o'N.); Karesuando (68 2o'N.). mer and winter temperatures became smaller up to the 1930*8, or in other words, up to that time the climate had shown a definite tendency to become more maritime. This is fully confirmed by the curves published by the late A. Labrijn 42 showing the difference between the mean temperature of July and that of the preceding January, in 14 places throughout Europe, for the period from 1750 until 1945. The same trend was clearly marked in Lenin- grad, Stockholm, Edinburgh, and Lancashire (England). Since the 1930*8 however, it has been reversed. It is worth noting that Paris, Prague, Vienna, and Budapest do not show a parallel tendency before the 1930*5 but since that time the reversed trend (i.e. towards a more continental climate) has been prominent. Moreover, most other places, and even subpolar regions, provide evidence that the pre- sent climatic improvement culminated during the 1930*5 or 1940'$. Curves giving ten-year overlapping mean temperatures from several stations in Sweden (Fig. 7) show that the in- crease in winter temperatures ceased with the 1930'$ and was succeeded by an equally clear decrease. At some sta- tions the January temperatures in the latest decade are lower than they have been at any time since the turn of the century. In Stockholm they have not been lower since 1 860. Of course the remarkably cold winters of 1 940, 1 94 1 , and 1942 play an important part in this decrease; yet even if overlapping means are calculated on the assumption that those winters had normal temperatures, a definite decrease is revealed. However, spring and even more autumn temperatures are still rising. In some parts of Sweden summer tempera^ tures also are rising, in other parts the maxinpiin has al-  ready been reached. It is particularly evident that the rise of summer temperatures in the glacier regions of north- western Scandinavia has culminated. At Karesuando and at Tromso (Fig. 8), for instance, July temperatures show continuous decrease since 1930-1939. In southern Sweden, in Lund and Stockholm for example, the maximum 'was reached only a few years ago or has not yet been reached. The annual mean temperature is still showing a rising trend. FIG. 8 Seasonal tem- perature anomalies from ^ Q the 1901-30 mean value at Tromso, Norway (66 gg 40- N.). On the right lo-year 0.4 overlapping anomalies; below, 3o-year overlap- Q ping anomalies. Notice the great difference be-- 0.4- tween the two groups of curves. 0-8 - Winter Spring Summer Autumn 1899-1908 1909-1918 1919-1928 1929-1938 1939-1946 0.8- 0.6- 0.4- 0.2 0- 0.2 0.4 .| 0.6 Winter Spring Summer Autumn 0.8 1856-1885 1866-1895 1876-1905 1876-1915 1896-1925 1906-1935 1916-1945 [*6] - -* -* FIGS, g and 10 Overlapping 10- year temperature anomalies in Ice- land from the mean value 1901-30. Figure 9 (left) is for Reykjavik. (64 10' N.); Figure 10 (right) is for Grimscy (66 30' N.). At Reykjavik in Iceland (Fig. 9) the climatic improve- ment culminated in the 1 940*5 and was succeeded by a deterioration, particularly in spring and autumn tempera- tures. But winter and average annual temperatures are still much higher than they were in the years preceding 1925-1930. The high temperatures recorded since 1890- 1900 in all seasons at Grimsey on the north coast (Fig. 10) are still being maintained. In the United States the decade 1 94 1-1 950 seems to have been characterized by lower temperature and increased precipitation in comparison with the decade 1931-194O. 43 From many points of view both scientific and practical it is thus of great importance that we should follow, care- fully and systematically, the climatic developments of the near future. This applies especially to the polar and sub- polar regions.  CAUSES OF THE RECENT GLACIER RECESSION AND THE PRESENT CLIMATIC FLUCTUATION The coincidence in time of the recent glacier recession and the present climatic fluctuation suggests a causal con- nection between them. I have come to the conclusion that increased ablation, consequent upon the increase in tem- perature, has played the fundamental role in the recession of glaciers around the northernmost Atlantic. I also find it probable that the rise in spring and autumn tempera- tures, i. e. the lengthening of the ablation season, has been of particular importance. As I have said before, 44 "The great shrinkage and recession of the glaciers is to a pre- ponderating extent due to an increased transfer of heat through the atmosphere by a strengthening of the winds carrying heat from southern parts to the Arctic." The dis- cussion about the meteorological causes of the present cli- matic fluctuation that is still going on has for the most part supported this general thesis. Twenty-five years ago Wagner explained the current climatic fluctuation by increased general atmospheric circulation with an increased exchange of heat and other atmospheric elements between northerly and southerly latitudes. 45 More recently B. E. Eriksson 46 found the most important feature of this fluctuation over the northern- most Atlantic to be a change in the pressure gradient causing an increased flow of warm air into northern lati- tudes. Willett 47 introduced the terms "high-index" and "low-index" to characterize two quite different types of circulation in the middle latitudes. With the "high-index" circulation cyclones move in winter in a strong zonal flow on fairly northern tracks from the Atlantic towards north- western Europe giving mild southwesterly to westerly  winds. The "low-index" circulation is characterized by a meridional flow pattern with the winter cyclonic tracks shifted southward giving cold easterly and northeasterly winds over most of Europe. However, Petterssen 48 has shown that "a warming up of northern latitudes in winter during the 1930*5 has been connected with a development towards another type of 'low-index' circulation pattern where the zonal components are also weak and the north- south components dominate." Instead of an increased zonal flow over northwestern Europe there has been a more meridional type of flow pattern giving rise to an increase in the northward transport of air from southern and east- ern Central Europe towards Scandinavia; and simultane- ously an increased northward transport of air from the eastern Atlantic towards Iceland and the Norwegian Sea. Partly in contradistinction to my own opinion is Wal- len's belief' 9 that the most important cause of the retreat of the Karsa Glacier during the last decades and probably of other glaciers in Scandinavia has been the rise of the summer temperature, 50 with prolongation of the ablation season of secondary importance. Wallen says: 51 "The es- sential cause for the regression and shrinkage in recent decades has been the increase for the heat supply from the air conveyed by convectional, conductional and conden- sational processes . . . there has also been a definite rise in the moisture content of the air ... and it is likely that the average wind-velocity has increased." In an article in preparation Wallen shows that the increase of southerly winds towards northern Scandinavia and the Arctic during the last 40 years is true not only for winter, as Petterssen pointed out, but also for summer. Referring to Petterssen's interpretation he concludes: "The increased general circu-  lation in recent decades has given rise to an increased ex- change of air between north and south over the Atlantic- European sector of the hemisphere. Both in winter and summer there has been an increased frequency of winds with a southerly component with a corresponding increase in temperature, humidity and cloudiness but giving no appreciable increase in winter precipitation." The "blocking-action" over western Europe 52 which has occurred quite often during recent decades and which has given rise to warm southerly and southwesterly winds over Scandinavia may well have contributed to glacier retreat. The opinion seems to be gaining ground among meteor- ologists that both brief fluctuations and long-range changes of climate, including the Pleistocene glaciations, are of the same general character and are ultimately dependent upon solar variations. In an article on the general circulation of the atmosphere Petterssen 53 points out "that the radiative processes, in tending to establish radiative equilibrium, create dynamic instability which gives rise to meridional circulations that contribute to the exchange of heat and atmospheric properties." He emphasizes the importance of mountain ranges, inland water bodies, etc. in the forma- tion of local circulation systems. A large-scale statistical analysis of the behavior patterns of cyclones and anti- cyclones in the northern hemisphere during the period 1 899- 1939 shows agreement between his theoretical re- sults and existing conditions, thereby giving scientific sup- port to the old ideas of the importance of mountain chains and orographically active epochs to the climate in past ages. 54 Petterssen's circulation models for the lower part of the troposphere in the northern hemisphere reveal an even  greater similarity in the dynamic-meteorological and climatological character between Alaska and western Scandinavia than has been presumed earlier. D. E. Martin, in an unpublished communication, confirms this by show- ing that positive and negative anomalies of the 700 milli- bar surface over Scandinavia are more directly related to similar anomalies in the Alaskan-Aleutian region than they are to anomalies elsewhere. Willett in his study of temperature trends has gone a step further. He maintains that changes in the ultraviolet part of the solar spectrum are not only causing the present climatic fluctuation but have also caused the great and small climatic changes of the past. Time will show whether his theory survives better than its predecessors. His idea has the advantage over most others in that the ultraviolet solar radiation varies more than the total radiation of energy. According to Willett, the present amelioration of the climate has now come to an end, and the temperature will fall for the next i o or 15 years, reaching a minimum between 1960 and 1965. Whatever the future may bring, we are justified in say- ing that of the endless series of climatic fluctuations that have occurred from the beginning of the earth and that will continue in the future, the present one is the first that we can measure, investigate, and possibly explain. CHANGES IN ARCTIC DRIFT ICE AND IN ANIMAL AND PLANT LIFE The thickness of the ice forming annually in the North Polar Sea has diminished from an average of 365 centi- meters at the time of Nansen's Fram expedition of 1893- 96 to 218 centimeters during the drift of the Russian icebreaker Sedov in 1937-40. The extent of drift ice in Arctic waters has also diminished considerably in the last decades. According to information received in theU.S.S.R. in 1945, the area of drift ice in the Russian sector of the Arctic was reduced by no less than 1,000,000 square kilo- meters between 1924 and 1944. The shipping season in West Spitsbergen has lengthened from three months at the beginning of this century to about seven months at the beginning of the 1940'$. The Northern Sea Route, the North-East Passage, could never have been put into regular usage if the ice conditions in recent years had been as difficult as they were during the first decades of this century. The same influences that have affected the drift ice have affected the animal life of the North Polar Sea. Various kinds of fish, especially cod, have migrated northwards. Now for the first time cod is available to many Greenland Eskimos who previously had to rely on seal for food. 55 In a speech five years ago the Danish Prime Minister said: "In the last generation changes that have had a decisive influence on all social life have occurred in Greenland. A new era has begun. These changes are primarily due to two circumstances. Firstly, the Greenland climate has changed, and with it Greenland's natural and economic prospects/' 55 On the other hand, herring catches off the north coast of Iceland have greatly diminished in the last seven years, possibly because of changes in the sea currents connected with the present climatic fluctuation. Herring has become an open sea fishery; its 1952 season was extended to No- vember instead of ending as usual in August. [3*] It is such phenomena that caused the International Council for the Exploration of the Sea to adopt the follow- ing resolution at its meeting in Denmark in 1948: "Having considered a number of lectures on climatic fluctuations, the Council recommends that these important and far- reaching problems ought to be more closely investigated, and that these investigations might be adequately sup- ported by the Governments in the different countries." 57 Many land animals in northern Europe and Asia are now ranging farther north than before. The migration seems to have begun slowly at the end of the eighteenth century, but has been greatly accelerated since 1910. Birds in particular have reacted quickly and markedly to the present climatic fluctuation. According to a report I have recently received from C. Edelstam of Stockholm, careful observation shows that about 25 per cent of all North- European bird species have taken part in this movement. The causes are two-fold: throughout the northern regions winters have been milder and springs warmer. At the same time lakes and bird-feeding grounds in large parts of Africa and southwest Asia have dried up. As a result, southern species dependent on shallow eutrophic waters are strongly represented in the migration. Effects of the present climate fluctuation are seen to advantage in Finland, a country of marginal location. On the initiative of I. Hustich, the Geographical Society of Finland has just published a symposium on the phenome- na, 58 studied from a biological and biogeographical point of view and embracing effects on forestry, agriculture, fish- ing, and hunting. In the first place, it has been observed that the freezing period in the Baltic decreased during the 1 20 years before  the 1930*8, after which a return to a longer freezing period began. This later climatic deterioration culminated in the beginning of the 1 940*5. Since then there has been a rise in winter temperature, resulting in a longer navigation period. 59 Floristically there has been a distinct shift towards earlier flowering and earlier ripening of berries and other seeds, and towards later defoliation. Ranges of plants and trees have expanded northwards, with attendant disturb- ance of species equilibrium in the plant communities. Effects on the coniferous forests are of particular in- terest. Between 1910 and 1920 the average annual ring index increased in all parts of Finland, especially in north- ern districts. Analyses of annual rings, which date back over 200 years, show scarcely any other period as favorable as the 1920*8. The significance of the change in climate, par- ticularly of the higher temperatures, is even more clearly indicated by the northern timber line. About 40 years ago the outlook for the northernmost pine forests was rather poor, as there had been no seed years there since 1850. Now, almost all age classes are represented in the seedling stands (PL III A). Hustich himself shows the importance of the climatic factor in the increase in the yield of rye, the commonest cereal, in the period 1921-1939. Birds have reacted in the same general manner noted for northern Europe as a whole. In Finland many species of mainly northern distribution have become scarcer at their southern limits, and the accidental species found in 1880-1941 have mainly been newcomers from the south. Contributions from other countries have been limited to specialized studies and scattered observations. I think,  however, that in Sweden and Norway the effects may on the whole be said to be similar to those in Finland. A critical analysis of the very extensive Swedish material on annual rings in pine and spruce, though not yet complete, justifies the statement that the present climatic fluctuation with its consequent prolongation of the growing season has probably helped towards the gradually increasing yield of the Swedish forest, as B. Eklund of the State In- stitute of Forestry Research has described in correspond- ence with me. Changes in the vegetation, as in Finland, are more marked in the far north, for instance, in the Abisko Na- tional Park (68 20' N.), undoubtedly because there the temperature has on the average risen more than in south- ern Sweden. Peat hummocks containing ice, the so-called Raises, a typical subpolar phenomenon, have been de- stroyed by melting of the ice. 60 The timber line for moun- tain birch has risen about 20 meters during the last decades and the surrounding vegetation has extended and become much richer (PL IV), especially during the 1940*5; partly, it seems, because of the earlier disappearance of the snow cover and the quicker drying of the soil. Sparse pine stands that formerly averaged only one new generation a century have added several new generations since the 1920*5. Dur- ing the iggo's in particular, regeneration was unusually rapid. 60 An investigation into the water economy of eight catch- ment areas in various parts of Sweden from 1920 to 1947 shows that evaporation has increased markedly since about ig 3 o. 61 In most parts of Norway, as in Sweden, the timber line has risen during the last decades. Among the several causes  are the reduction or discontinuance of lumbering in the uppermost parts of the birch and coniferous belts and the reduction of grazing and reindeer keeping. All students of the problem agree, however, that an improving climate has played an important part in accentuating the consequences of such cultural conditions, most especially in northern Norway. 62 In a recent communication, R. Sognen, of the Nor- wegian Watercourse and Electricity Board, points to an unfortunate effect that might follow continuance of the present trend. Continued and rapid recession of glaciers might prove fatal to some of the Norwegian power genera- ting stations, for it would reduce the quantity of water which the ice has stored for centuries and upon which the stations partly depend for their supply. The present climatic fluctuation has been even more marked in Iceland than in the other Nordic countries and its influence on local plant and animal life is perhaps more apparent than in any other region. A few of the current and still continuing changes may be noted: The peat and ice hummocks, rusts, (same type as the poises of Lapland), which characterize the marshes, fids, in the interior of Ice- land (PL III B), are gradually disappearing under the milder climate. The whole landscape, in fact, is changing. 63 There has been a rise in the lower fid limit; it corresponds with the northward recession of the southern limit of the Siberian permafrost zone. In this connection, attention may also be drawn to the so-called "oriented lakes" 64 of northernmost North America created by melting of the permafrost. Because of Iceland's geographical position, elements of both southern and arctic faunas live there under peripher-  al conditions and react quickly to climatic changes. Seven new southern species of birds have begun breeding in Ice- land within the last 50-60 years, there has been a consider- able increase in the wintering of partly non-migratory species, and there has been a very noticeable increase in winter visitors and vagrants from the south. No less than 37 new species or subspecies of birds have been added to the Icelandic list since 1938, and at the same time some of the few arctic and high-arctic species have disappeared. 65 THE PRESENT CHANGE IN THE SEQUENCE OF CHANGES How then do the present climatic fluctuation and the recent glacier recession compare with conditions in earlier centuries and millenia? How do they fit into the progres- sion since the melting of the Pleistocene glaciers? The two curves of Figure 1 1 are plotted to illustrate our present conception of the sequence in Sweden 66 and Nor- way 67 from about 8000 B.C. to 1950 A.D. The glacier-varia- tion scale is relative and the time scale logarithmic, in order to show clearly the recent centuries and decades of time, which are, of course, the best known. The third, dashed curve, gives the position of the firn or climatic snow line on Vatnajokull, Iceland, according to Eythorsson. 68 In the lake district of south Sweden, and within the present coastal region of Norway, the waning inland ice re-expanded in about 8000 B.C. It subsequently retreated under the improving climatic conditions. The economic regime of the Ice Age, which year after year provided a surplus of snow, had long since been abandoned. The rest of its immense capital of ice was consumed by a milder  regime, more favorable to mankind. The Climatic Opti- mum occurred between about 7000 B. C. and about 1000 B. C. In that epoch the firn line of Vatnajokull is estimated to have been at about 1400 meters above sea level. Studies wieiers 3500 k k 3000- xBothnian glacial substage (End moraines) 2500- GLACIER VARIATIONS, SWEDEN Meters above 2000- (E. Bergstrom) Climatic Optimum sea level -1400 1500- 1200 -1000 1000- 800 500- 0- _y ^ v -~-^_ 600 v/v/ 8000 5000 1000 1000 1600 1750 1900 1950 GLACIER VARIATIONS, NORWAY (O. Liestol) v FIRN LINE, VATNAJOKULL, ICELAND 8000 5000 1000 1000 1600 1750 1900 1950 FIG. 11 The recession of the last Pleistocene inland ice from Sweden and Norway and the variations of the local Scandinavian glaciers during the last 12,000 years. For sources see footnotes 66 and 67. of peat bogs in Sweden have shown that there were prob- ably changes, in atmospheric humidity at least, in about 2300 and 1200 B.C. The subsequent deterioration of the climate culminated in about 500 B.C. and the firn line of Vatnajokull dropped to 500-600 meters. That climate still exists even if it has improved somewhat during certain  times. There is no evidence in either Sweden or Norway of any glacier variations or climatic changes during the following 2000 years, except in the favorable Roman period (A.D. 0-400). We know, however, as has been mentioned before that from the first colonization of Ice- land in A.D. 870 until about A.D. 1200 the glaciers were much smaller than they are now. The Vatnajokull firn line is calculated as having been at about 1 100 meters at that time. From the latter part of the i7th century right up until the latter part of the i gth and the beginning of the soth century, glaciers both in Iceland and on the con- tinent of Europe were more extensive than at any time since the melting of the last remnants of the Pleistocene inland ice in the Scandinavian mountains. The Vatna- jokull firn line dropped to its minimum. The recent gla- cier recession, which began earlier in some districts and later in others, has in the last few decades reduced the glaciers so much that they are now probably as small or even smaller than they were in Roman time. The Vatna- jokull firn line has risen successively to its present altitude of about 1 100 meters above sea level. Thorarinsson's studies of the past and present cultiva- tion of cereals in Iceland have shown that in recent years climate there has been at least as favorable, and probably even slightly milder than it was in the centuries imme- diately after A.D. goo, and it is warmer now than at any time since isoo. 69 According to Thorarinsson, the ampli- tude of the climatic fluctuation in Iceland has in all proba- bility been greater since the i88o's than at any time since about 600 B.C. It has already been pointed out (p. 18) that the present position of the termini of some glaciers in southern Ice-  land ought to be about the same as in the last part of the seventeenth century. They are however much more ad- vanced than in the time of the Sagas (A.D. 870-1264). The position of the farms Fjall and Breida (Fig. 4) is not known exactly but must have been close to that shown. They were probably built around A.D. 900, and cannot at that time have been in a dangerous position to a glacier front or to drainage of ice-dammed lakes. Yet Fjall was aban- doned in 1695 and buried by the glacier in 1708. Breidd was a large farm until the fourteenth century, but in 1698 it also was abandoned and in 1702 the glacier front had almost reached it. Thorarinsson points out that the de- cline of Breida is not only a result of the deterioration of the climate but also largely of the eruption of the volcano Oraefijokull in about 1360. It seems, he says, that this cli- matic deterioration had already begun in the thirteenth century, accelerated in the fourteenth, and culminated during the seventeenth to nineteenth centuries. These conclusions from Iceland agree with some con- clusions from Greenland. It is hardly possible that the climate of southwest Greenland could have been so severe when the Norse colony there was an independent society with about 300 farmsteads, 3000 people, and a surprisingly large number of cattle and sheep, as it was some decades later. 70 In 1921 excavations of the cemetery at Herjolfsnes yielded well-preserved clothing from about the year i4oo. 71 Interment must have been in loose earth but preservation was possible because the ground was frozen soon after the interment. 72 Concerning the Alps, Kinzl 73 has come to the conclusion that the glacier advance of the last 300 years is the greatest that has occurred since the Pleistocene Ice Age. "Those  300 years therefore/' says Matthes, 74 * 'comprise a separate epoch of glacier expansion, a lesser ice age, that was pre- ceded by a warm period of considerable duration/' It is worth while reflecting that our modern machine culture was born and has grown up under climatic conditions even more unfavorable, certainly, than those which extended since Celtic time, i.e., since the Persian wars and Classical Greek time. In large areas of North America, as has been mentioned before, a strong glacier advance attained its maximum in the first half of the i8th century. It also was the maximum state of advance since the twelfth century. Matthes has characterized the period of the last 4000 years as "the little ice age/' I am more inclined to say: Regeneration of the glaciers began in about 500 B.C.; after some centuries of rapid increase growth was slower until the thirteenth or fourteenth centuries when it again accel- erated and so far has reached its climax in most districts between the first half of the eighteenth century and about 1900. However, in front of some glaciers, for example some of Vatnajokull and Myrdalsjokull in Iceland, there are ter- minal moraines which might indicate that in early "sub- atlantic" time (the first centuries about the beginning of our era) these glaciers advanced a little further than during the last few centuries. 75 In front of several glaciers in the high mountains of Sweden there also is one morainic ridge just outside those representing the maximum extension about 1750 and much older. Similar examples occur in southern Norway 76 and in the central Alps. 77 SOME ASPECTS OF THE FUTURE I have tried in this lecture to give you a brief outline of our present knowledge of recent glacier variations and the present climatic fluctuation, based chiefly on facts estab- lished in the Nordic countries and to a lesser extent in North America. I have also tried to project these phe- nomena against the background of what Scandinavian stu- dents consider the most likely progress of the melting of the inland ice and the most likely local glacier variations in the last 10,000 years. Our results are most certainly in- complete and in some, perhaps many, respects may prove to be erroneous. But in the treatment of these and of many other problems a new epoch is now opening before us. A few examples will suffice. Its new-found geophysical basis has made glaciology bet- ter able to explain the reactions of glaciers to meteorologi- cal factors. We hope to be able to organize international cooperation for the purpose of getting accurate values of representative glacier regimes for elucidating glaciological- climatic development in the subarctic zone. The glaciers ought to be not too big but should be well defined. So far the following glaciers have been selected: Lemon Creek Glacier in southern Alaska (near Juneau), a glacier in the Tindfjallajokull group in southern Iceland, Stor Glacier in Jotunheim in southern Norway, and Stor Glacier in the Kebnekajse Massif, northern Swedish Lapland. If possible we want to include a glacier in northernmost Greenland. The investigations and measurements are planned to be of the same kind as those of Stor Glacier in Kebnekajse. Improved statistical methods of analysis will eventually provide a more assured and detailed picture of long-range climatic fluctuations. New methods of age determina-  1*1. I A Karsa Glacier, south ot Abisko Toinisi Station in Swedish Lapland (68 so'N.). Photo C. C. Walk'n. it)|S. PI. I B Stor Glacier, Kcbnekajse Massif, Swedish Lapland (675o'N., 2117 meters above sea level). In the background the highest elevation, Sycltopp, covered by a small glacier. Photo G. Lundquist, August, 1951. PI. II ABukkho Glacier, Jotunheim, Norway (61 4(>'N.), 19-19. The dotted line shows the glacier extension in about 1750. Photo O. Liestol, 1919. PI. II B Engabre Glacier, an outlet glacier from the Svartiscn glacier cap, Not way (66 [o'), in 1919; in 1930 the glacier still covered most of the lake. 1*1. Ill A Twenty-ihice xear old and \ounger pines in the mountain biuli forest at Fnontekio in Finland (68 $o'N.). Photo h\ P. Mikola. if) 19. 1*1. Ill 11 A mature pals (tailed rust in hel.md), in a flti soutli ol llofsjokull Iceland (6.4 <jo'N.); it is (mo in. .ihoM 1 sea lex el. 10 in. long, and neailx ij in. high. Photo by F. (iudinnnd.s.son, 1*151. PI. IV A Timber line on Lapland (68 2o'N.). in 1937; the eastern slope oi Njulja, Abisko, ) in 19*8. Photo G. Sandberg. Swedish tion, notably by radiocarbon content, will in conjunction with continued paleobotanical research throw a new and stronger light on the climatic changes of the past thirty thousand years. The results of the Swedish Oceanographic Expedition of 1947-1948 promise to be of great impor- tance to our understanding of the same phenomena throughout a much longer period of the world's history. I have claimed your attention in order to sum up some of my thoughts on the state of our knowledge of snow, ice, and climate in selected areas of the world, as well as some scattered features of changes in the flora and fauna due to the present climatic fluctuation. I have done so not only because an account ought to be given of our observations and results, even though the conclusions may soon be out- of-date, but also and of greater moment for this gathering to direct your attention to the many relevant problems, and to stimulate continued work towards their solution by the newer and better methods which this constantly developing science brings forth. For climate, its changes and fluctuations, is, as Isaiah Bowman has said, a funda- mental factor in physical geography and one of the most important influences on the phenomena to which human geography is devoting its attention.  FOOTNOTES 1 Isaiah Bowman: Geography in the Creative Experiment, Geogr. Rev., Vol. 28, ^S 8 * PP- 1 ~ 1 9- 2 G. M. Wrigley: Isaiah Bowman, Geogr. Rev., Vol. 41, 1951, pp. 7-65. 3 H. W:son Ahlmann: The Contribution of Polar Expeditions to the Science of Glaciology, Polar Record, Vol. 5, 1949, pp. 324-331. 4 The results of Expeditions Polaires Franchises (Missions Paul-mile Victor), in Publications preliminaries (mimeographed) and in Resultats sci- entifiques (Actualit^s scientifiques et industrielles, Hermann et Cie, Paris). s Popular narratives of the expedition are: John Giaever: Maudhcim: To ar i Antarktis Oslo, 1952); John Giaever och Valter Schytt: Antarktisboken: Med Norsel till Maudheim och Antarktis (Stockholm, 1952). English and American editions will follow. Preliminary scientific reports are: E. F. Roots: The Norwegian-British-Swedish Expedition 1949-52, Science News, No. 26, Penguin Books, 1952, pp. 9-32; G. de Q. Robin: Measurements of Ice Thickness in Dronning Maud Land, Antarctica, Nature, Vol. 171, 1953, pp. 55-58; The Norwegian-British-Swedish Antarctic Expedition, 1949-52. I. Valter Schytt: Summary of the Glaciological Work; II. G. de Q. Robin: Summary of Seismic Shooting Investigations in Dronning Maud Land, Journ. of Glaciol, Vol. 2, No. 13, 1953, pp. 204-205; 205-213. 6 Quoted in a debate at the Seventeenth International Geographical Congress in Washington, D. C., August, 1952, in "Premiers Enseignements Glaciologiques des Expeditions Polaires Franchises 1948-1951." 7 H. W:son Ahlmann: Glaciological Research on the North Atlantic Coasts, Royal Geogr. Soc. Research Ser. No. i, 1948, reference on pp. 66-67; idem: The Contribution of Polar Expeditions, op. cit., p. 327. 8 R. P. Sharp: Accumulation and Ablation on the Seward-Malaspina Glacier System, Canada-Alaska, Bull. Geol. Soc. of America, Vol. 62, 1951, pp. 725-743. 9 H. U. Sverdrup: The Scientific Results of the Norwegian-Swedish Spits- bergen Expedition in 1934, Part IV, The Ablation on Isachsen's Plateau and on the Fourteenth of July Glacier in Relation to Radiation and Meteorological Conditions, Geografiska Annaler, Vol. 17, 1935, pp. 145-166. 10 C. C. Walle*n: Glacial-Meteorological Investigations on the Karsa Glacier in Swedish Lappland 1942-48, Geografiska Annaler, Vol. 30, 1948, pp. 451-672. 11 Idem: Influences Affecting Glacier Extension in Northern Sweden, Union Gdodesique et Gdophysique Internationale, Assoc. Internatl. d'Hydrologie Sci., Assemble Ge'n. de Bruxelles 1951, Vol. i, Louvam, 1952. "H. W:son Ahlmann and Sigurdur Thorarinsson: Vatnajokull: Scientific Results of the Swedish-Icelandic Investigations 1936-37-38, Chapter V, The Ablation, Geografiska Annaler, Vol. 20, 1938, pp. 171-233 (see also the Geogr. Rev., Vol. 28, 1938, pp. 412-438); H. W:son Ahlmann: Vatnajokull, Ch. VII, The Regime of HofFellsjokull, Geografiska Annaler, Vol. 21, 1939, pp. 171-188. *3 B0rge Fristrup: Climate and Glaciology of Peary Land, North Greenland, Union Ge'odesique et Geophysique Internationale, Assoc. Internatl. d'Hydro-  logie Sci.j Assemblee Gen. de Bruxelles 1951, Vol. i, Louvain, 1952; idem: Danish Expedition to Peary Land, 1947-1950, Geogr. Rev., Vol. 42, 1952, pp. 87-97- J 4 H. W:son Ahlmann: Scientific Results of the Swedish-Norwegian Arctic Expedition in the Summer of 1931, Part VIII, Glaciology, Geografiska Annaler, Vol. 15, 1933, pp. 161-216 and 261-295, reference on pp. 181-186 (Marginal Movements in the Spitsbergen Glaciers); idem: Scientific Results of the Nor- wegian-Swedish Spitsbergen Expedition in 1934, Part V, The Fourteenth of July Glacier, ibid., Vol. 17, 1935, pp. 167-218. J 5 E. F. Roots, op. cit. *6p. D. Baird: The Glaciological Studies of the Baffin Island Expedition, 1950, Part I, Method of Nourishment of the Barnes Ice Cap, Journ. of Glacial., Vol. 2, No. 11, 1952, pp. 2-9. !7 F. E. Matthes: Glaciers in Hydrology, Physics of the Earth IX, New York, 1942, pp. 149-219. 18 Scientific Investigations in the Kebnekajse Massif, Swedish Lappland, Parts I-IV published to date, Geografiska Annaler, Vol. 33, 1951, pp. 90-143. Pre- liminary reports are: Valter Schytt: Glaciologiska arbeten i Kebnekajse, Ymer, Vol. 67, i9t7 pp. 18-42; H. Wrson Ahlmann: Kebnekajse, Svenska Turist- foreningens Arsskrift 7952, Stockholm, 1952, pp. 265-288. *9 W. O. Field, Jr. and M. M. Miller: The Juneau Ice Field Research Project, Geogr. Rev., Vol. jo, 1950, pp. 179-190; M. M. Miller and W. O. Field: Explor- ing the Juneau Ice Cap, Research Reviews, Office of Naval Research, Dcpt. of the Navy, Washington, D. C., April, 1951; R. P. Sharp, of), cit. Progress Report, Juneau Ice Field Research Project, Alaska, 1952. Prepared by A. K. Gilkey with Summaries of Research Work by Members of the Project (mimeographed). Amor. Gcogr. Soc., January, 1953. * Erik Woxnerud: Scientific Investigations in the Kebnekajse Massif, Part IV, Det lokala triangelnatets i Kebnekajse ansluning till riksnatet. Syd- och Nordtopparnas hojd over havct (The linking up of the local triangulation net in the Tarfala Valley with the official geodetic net. The heights above sea level of the Sydtopp and the Nordtopp), Geografiska Annaler, Vol. 33, 1951, pp. 131-143. 21 The Swedish curve is plotted by E. Bergstrom, Stockholm, on the basis of his studies in the Swedish glacier districts and of his comparative studies in Norway. Of great importance to his chronology has been the identification of three different zones of vegetation cover, which arc represented especially by lichens. The boundary of each zone appears to correspond to the position of the ice margin at a time when the glacier extended as far as one of the principal old terminal moraines. The Norwegian curve relates to the Nigardsbre, an outlet glacier from Jostedalsbre, which may be regarded as being representative of the glaciers of southern Norway. The values are plotted by O. Liestol, of the Norwegian Polar Institute, from Knut Faegri: Ober die Langenvariationen einiger Glet- scher des Jostedalsbre und die dadurch bedingtcn Pflanzensukzessionen, Bergens  Museums Arbok 1933, Naturvidenskapelig rekke, No. 7, Bergen, 1934; idem: On the Variations of Western Norwegian Glaciers During the Last 200 Years, Procds-Verbaux des seances de I'AssembUe Gen. d'Oslo de I'Union Geodesique et Geophysique Internationale, Louvain, 1948; and from consecutive measure- ments carried out by the Norwegian Polar Institute, Oslo. 22 The Drangajokull. curve is based upon Jon Eyth6rsson: On the Variations of Glaciers in Iceland, I, Drangajokull, Geografiska Annaler, Vol. 17, 1935, pp. 121-136, and for later years on Eythorsson's measurement of four outlet glaciers from the ice cap, plotted together by Sigurdur Thorarinsson. The Vatnajokull curve is based upon Eythorsson's measurements of about 18 of the southern outlet glaciers on the ice cap, summarized to the year 1930, by Thorarinsson in Vatnajokull, Chapter XI, Oscillations of the Iceland Glaciers in the Last 250 Years, ibid., Vol. 25, 1943, pp. i~54, and after that year supplemented by him. 23 M. Mougin: Glacier des Bossons, tudes glaciologiques en Savoie in tudes glaciologiques, Service des Forces Hydrauliques, Vol. 3, Paris, 1912, and Vol. 5, Paris, 1925; and Rapport sur les variations de longeur des glaciers de 1913 a 1928, Commission des glaciers, Union Ge"ode"sique et Geophysique Interna- tionale, Venice, 1930. After 1925 there are sporadic measurements published in Commission des glaciers, U.G.G.I. They are, however, sufficient to allow plotting of the dashed part of the curve. The rapid recession of the last few years parallels conditions in other parts of the Alps. The curve is plotted by O. Liestol, Oslo. 24 Plotted by the author from: D. B. Lawrence: Glacier Fluctuation for Six Centuries in Southeastern Alaska and Its Relation to Solar Activity, Geogr. Rev., Vol. 40, 1950, pp. 191-223; idem: Glacier Fluctuation in Northwestern North America during the Past Six Centuries. Proce's-Verbaux des seances de I' As- semblee Gen. d'Oslo de I'Union Geodesique et Geophysique Internationale, Louvain, 1948; and from H. W. Mathews: Historic and Prehistoric Fluctua- tions of Alpine Glaciers in the Mount Garibaldi Map-Area, Southwestern British Columbia, Journ. of GeoL, Vol. 59, 1951, pp. 357-380. 25 Ad. S. Jensen and B0rge Fristrup: Den arktiske klimaforandring og dens betydning, sacrlig for Gr0nland, Geogr. Tidskrift, Vol. 50, 1950, pp. 20-47 (see also W. R. B. Battle: Contributions to the Glaciology of North East Greenland 194849 in Tyrolerdal and on Clavering 0, Meddelelser om Gr0nland, Vol. 136, No. 2, 1952, pp. 1-26 (second section). 26 H. W:son Ahlmann: Studies in North-East Greenland, 1939-40, Part II, Glacial Conditions in North-East Greenland in General and on Clavering Island in Particular, Geografiska Annaler, Vol. 23, 1941, pp. 183-209. For observations in 1947, see Ad. S. Jensen and B0rge Fristrup, op. cit. Charles Swithinbank carried out investigations here during the Norwegian Polarbjorn expedition, 1952. 27 p. D. Baird: The Baffin Island Expedition, 1950, Geogr. Journ., Vol. 118, 1952, pp. 267-279. 28 See also Sigurdur Thorarinsson: Vatnajokull, Chapter XI, op. cit., and "1 veldi Vatnajokuls," I in Lesb6k Morgunblathsins 1946, Reykjavik, 1946.  2 9 Rapport sur les variations de longeur de glaciers europ6ens de 1947 a 1950, Union Geodesique et Geophysique Internationale, Assoc. Internatl. d'Hydro- logie Sci., Assemblee Gen. de Bruxelles 1951, Vol. i, Louvain, 1952. 30 A review of these oscillations up to 1940 is given by F. E. Matthes, op. cit.; A. E. Harrison: Ice Advance during the Recession of the Nisqually Glacier, Mountaineer, Vol. 43, Dec., 1951, pp. 7-12. 31 D. B. Lawrence, op. cit.; J. L. Dyson: Glaciers of the American Rocky Mountains, Triennial Report, Committee on Glaciers, Section of Hydrology, American Geophysical Union (mimeographed), 1952. See also C. J. Heusser: Pollen Profiles from Southeastern Alaska, Ecological Monographs, Vol. 22, !952, pp- 33!-352- 32 W. O. Field, Jr.: Glacier Recession in Muir Inlet, Glacier Bay, Alaska, Geogr. Rev., Vol. 37, 1947, pp. 369-399. 33 See also R. L. Nichols and M. M. Miller: The Moreno Glacier, Lago Argentino, Patagonia, Journ. of Glaciol., Vol. 2, No. 11, 1952, pp. 41-50. 34 See also P. D. Baird: Report on the Northern American Glaciers, Union Geodesique et Geophysique Internationale, Assoc. Internatl. d'Hydrologie Sci., Assemblee Gen. de Bruxelles 1951, Vol. i, Louvain, 1952. A. E. Harrison (per- sonal communication) says that "the terrific recession characteristic of the twenties and thirties seems to have passed a climax." 35 A. E. Harrison: Ice Advance, op. cit., and Glacier Studies 1952 Sequel, Mountaineer, Vol. 44, 1952. In the latter he points out: 'In spite of two seasons of excessive melting and the loss of ice at the higher elevations on the glacier, the wave of ice reported last year (1951) is still making progress down the Nisqually Glacier. The accumulation of ice since 1944 is too great to be dissi- pated immediately." See also R. A. Dightman and M. E. Beatty: Recent Montana Glacier and Climate Trends, Monthly Weather Rev., Vol. 80, 1952, pp. 77-81. 3<5Sigurdur Thorarinsson: Present Glacier Shrinkage, and Eustatic Changes of Sea-Level, Geografiska Annaler, Vol. 22, 1940, pp. 131-159. See also, for instance, L. C. W. Bonacina and E. L. Hawkes: Climatic Change and the Retreat of Glaciers (with discussion), Quart. Journ. Royal Metcorol. Soc., Vol. 37, 19^7, pp. 85-95; R- F- Flin^ Climatic Implications of Glacier Research in Compendium of Meteorology, edited by T. F. Malone (Amer. Meteorol. Soc., Boston, 1951), pp. 1019-1023. 37 J. de Heinzelin: Glacier Recession and Pcriglacial Phenomena in the Ruwenzori Range (Belgian Congo), Journ. of Glaciol., Vol. 2, London, 1952, pp. 137-140. (This issue also contains references to articles about other African mountains which support glaciers.); E. Bergstrom: Som glaciolog p Ruvenzori (As Glaciologist on Ruwenzori, with an English Summary), Ymer, Vol. 73, 1953, pp. 1-23. 38 Sirri Erinc.: Glacial Evidences of the Climatic Variations in Turkey, Geo- grafiska Annaler, Vol. 34, 1952, pp. 89-98. 39 There is, however, "no proof of a general recession of south Patagonian glaciers during the last twenty years" (Louis Lliboutry: More About Advancing  and Retreating Glaciers in Patagonia, Journ. of GlacioL, Vol. 2, No. 13, 1953, pp. 168-172; reference on p. 172). 40 H. J. Harrington: Glacier Wasting and Retreat in the Southern Alps of New Zealand, Journ. of GlacioL, Vol. 2, 1952, pp. 140-145. 41 Leo Lysgaard: Recent Climatic Fluctuations, Folia Geographica Danica, Vol. 5, 1949 (with extensive bibliography); H. C. Willett: Temperature Trends of the Past Century, Centenary Proc. Royal Meteorol. Soc., 1950, pp. 195-206. Among numerous other studies of the present climatic fluctuation, the follow- ing may be mentioned: Anders Angstrom: Teleconnections of Climatic Changes in Present Time, Geografiska Annaler, Vol. 17, 1935, pp. 242-258. Idem: The Change of the Temperature Climate in Present Time, ibid, Vol. 21. 1939' PP- H9-13 1 - Idem: Nederbordsklimatets andring i nuvarande tid, Stat. Mct.-Hydro. An- stall, Meddelandcn, Serien uppsatscr, No. 37, Stockholm, 19 |i. II. W:son Ahlmann: Den nutida klimatfluktuationen, Ymcr, Vol. 61, 191 1, pp. 11-24. Idem: Den nutida klimatfluktuationen och Gronland, Del Gr0nlandske Selskabs Aarsskrift, 1947, pp. 9-38. Idem: The Present Climatic Fluctuation, Gcogr. Journ., Vol. 112, 1949, pp. 165-195- B. E. Eriksson: Till kannedomen orn den nutida klimatandringcn inom omradena kring nordligaste Atlanten, Geografiska Annaler, Vol. 25, 1913, pp. 170-201. J6n Eythorsson: Temperature Variations in Iceland, Geograjnka Annaler, Vol. 31, 1949, pp. 36-55. Th. Hesselberg and B. J. Birkeland: Siikulare Schwankungen des Klimas von Norwegen, Geofysiske Publikasjoner, Vol. 14, Nos. 4-6, Oslo, 1940-1913, and Vol. 15, No. 2, 1944. J. Keranen: Uber die Temperaturschwankungen in Finland und Nordcuropa in den letzten hundert Jahren, Finn. Akad. der Wissensch., Sitiungsber., IQJI, 1944- J. B. Kincer: Is Our Climate Changing? A Study of Long-Time Temperature Trends, Monthly Weather Rev., Vol. 61, 1933, pp. 251-259. Idem: Our Changing Climate, Trans. Amer. Geophys. Union, Vol. 27, 1946, PP- 342-347- A. Labrijn: Het klimaat van Nederland gedurende de laatste twee en een halve eeuw (With an English summary), Mededeling en Verhandelingen, Koninkl. Nederl. Meteorol. Imt., Vol. 49, No. 102, Gravcnhage, 1945. H. Landsberg: Climatic Trends in the Series of Temperature Observations at New Haven, Conn., Geografiska Annaler, Vol. 31, 1949, pp. 125-132. Idem: Some Recent Climatic Changes in Washington, D. C., Archiv fur Meteorologie Geophysik und Bioklimatologie, Ser. B., Vol. 3, Vienna, 1951, pp. 65-71.  L. B. Leopold: Rainfall Frequency: An Aspect of Climatic Variation, Trans. Amer. Geophys. Union, Vol. 32, 1951, pp. 347-357. G. H. Liljcquist: The Severity of the Winters at Stockholm 1757-1942, Geografuka Annaler, Vol. 25, 1943, pp. 81-101. Idem: On Fluctuations of the Summer Mean Temperature in Sweden, ibid., Vol. 31, 1919, pp. 159-178. Gordon Manlcy: Temperature Trend in Lancashire, 1753-1945, Quart, Journ. Royal Meteorol. Soc., Vol. 72, 1946, pp. 1-31. Idem: The Range of Variation of the British Climate, Geogr. Journ., Vol. 117, 1951, pp. 43-68. Idem: The Mean Temperature of Cential England, 1698-1952, Quart. Journ. Royal Meteorol. So( ., Vol. 79, 1953. Idem: Climatic Variation, ibid., pp. 185-209. [Note the bibliographical Sverre Petteisseu: Changes in the General Circulation Associated with the Recent Climatic Variation. Gcografiska Annaler. Vol. 31, 1949, pp. 212-221. F. Piohaska: /in Frage der Klimaandc-rung in Polar/one des Sudatlantiks, Arcliiv fur Meteoiologie Gcophystk ujid Biokltmatologie, Ser. B., Vol. 3, Vienna, 'OS 1 - PP- 7-- 81 - Mat tin Rodewald: Ruckgang dcr Klimaandeiung in den Vercinigtcn Staaten, Geograjiska Annaler, Vol. 34. 1952, pp. 159-167. E. Rubenstein: K piobleme i/minenija klimata, Ser. Hydjo-Meteorol. Serv- ice. Sci. Research Dept., Geophys. Centre, Leningrad, 1946. R Scherhag: Fine bemcrkenswertc Klimaandcrung uber Nordeuropa, An- nalen der Hydrogr. und Alarit. Meteorol.. Vol. 64, 1936, pp. 96-100. Idem: Die Fiwarinung des Nordlichcn Polargebiets, ibid.. Vol. 67, 1939, pp. 57- ( i7- A. Wagner: Klimaandcrungen und Klimaschwankungcn, Die Wissenschaft, Vol. 92, Brunswick, ig.jo. H. Winter: Anderungen im Sommerklima scit 150 Jahren. Archiv fur Mt'tcorologie Geophysik und Bioklitnatologie, Scr. B., Vol. 3, Vienna, 1951, pp. 82-90. ^A. Labrijn: Ondcr/oek naar Klimaatschommelingcn in het Stroomgebied van de Rijn, Mededeling van het Hedrijf der Gemeentewaterleidingen, No. 10, De Watervoor/iening van Amsterdam, Aanvullende Gegevens op Rapport, i91. 43 Mart in Rodewald, op. cit. 44 H. W:son Ahlmann: Glaciological Research, op. cit., pp. 77-78. 45 A. Wagner: Untersuchungrn der Schwankingcn der allgcmcine Zirkulation, Geografiska Annaler, vol. 11. 1929, pp. 33-82. 46 B. E. Eriksson, op. cit. 47 H. W. Willctt: Descriptive Meteorology, New York, 1944; idem: Long- period Fluctuations in the General Circulation of the Atmosphere, Journ. of MeteoroL, Vol. 6, 19-19. pp. 34-50. 48 Sverre Pctterssen, Changes in the General Circulation, op. cit.  49 C. C. Walln: Recent Variations in the General Circulation As Related to Glacier Retreat in Northern Scandinavia, Geofisica Pur a e Applicata, Vol. 18, Milan, 1950, pp. 3-6; idem: Glacial- Meterological Investigations, op. cit.; idem: Influences, op. cit. so G. H. Liljequist: On Fluctuations of the Summer Mean Temperature, op. cit. 51 Influences, op. cit. 52 D. F. Rex: Blocking Action in the Middle Troposphere and Its Effect Upon Regional Climate, Tellus, Vol. 2, 1950, pp. 196-211 and 275-301; Vol. 3, 1951, pp. 3-16. 53 Sverre Petterssen: Some Aspects of the General Circulation of the Atmos- phere, Centenary Proc. Royal Meteorol. Soc., 1950, pp. 120-155. 54 C. E. P. Brooks: Climate Through the Ages (rev. edit., London, 1949). 55 Ad. S. Jensen and B0rge Fristrup: Den Arktiske klimaforandring, op. cit. 56 Hans Hedtoft: Gr0nlands Fremtid, Det Gr0nlandske Selskabs Aarsskrift, 1949, pp. 22-42. In a lecture at Oslo in February, 1953, Director P. Rosendahl of the Greenland State Department in Copenhagen pointed out that the principal reason for the new era in Greenland has been the present climatic fluctuation with the associated disappearance of the seals and the northern migration of cod. 57 H. W:son Ahlmann: The Present Climatic Fluctuation, op. cit., p. 192. 58 The Recent Climatic Fluctuation in Finland and Its Consequences, Fennia, Vol. 75, Helsinki, 1952. 59 In an unpublished article C. C. Wallen has shown that from the period 18831913 to 1930-50 the temperature of the surface water in the Gulf of Bothnia rose as much as 2 C. in August, and little less in other months. A warming up of the water has also taken place in the southern part of the Baltic as well as on the west coast of Sweden. 60 G. Sandberg: Den pagaende klimatforandringen, Svenska Vall-och Mosskul- turforeningens Kvartalsskrift 1940, Uppsala, 1940; and his report to the author dated July, 1952. 61 F. Bergsten: Contribution to Study of Evaporation in Sweden, Sveriges Meteorol. o. Hydrol. Inst., Meddelanden Ser. D., Nr. 3, 1950. 62 S. Ve: Stig skoggrensa? Tidskrift for Skobruk, No. 9, Oslo, 1951, pp. 305- 317- 63 Sigurdur Thorarinsson: Notes on Patterned Ground in Iceland, with Particular Reference to the Icelandic "Flas," Geografiska Annaler, Vol. 33, 1951, pp. 144-15 6 - 6 4 R. F. Black and W. L. Barksdale: Oriented Lakes of Northern Alaska, Journ. of GeoL, Vol. 57, 1949, pp. 105-1 18. 6 5 Finnur Gudmundsson: The Effect of the Recent Climatic Changes on the Bird Life of Iceland, Proc. loth Internatl. Ornithological Congress, Uppsala 1950, Stockholm, 1951, pp. 502-514. 66 Plotted by E. Bergstrom. Before 1650 A.D. based principally on: F.A.D. Enquist: Die glaciale Entwicklungsgeschichte Nordwestskandinaviens, Sveriges GeoL Undersokning, Ser. C., Nr. 285, 1918. After 1650 A.D. on: Knut Faegri:  On the Variations of Western Norwegian Glaciers During the Last 200 Years, Proces-Verbaux des seances de I'Assemblee Gen. d'Oslo de ['Union Geodesique et Geophysique Internationale, Louvain, 1948; Axel Hamburg: Sarjekfj alien, Yrner, Vol. 21, 1901, pp. 145-204 and 223-276; N. H. Magnusson, E. Granlund, and G. Lundqvist: Sveriges geologi, 1949; A. Wagner: Klimaiinderungen und Klimaschwankungen, op. cit.; A. Walle"n: Om langvariga klimatforandringar och kallorna for deras utforskande, Popular Naturvetenskaplig Revy, Vol. 6, Stockholm, 1918; Anders Angstrom: Sveriges kliinat, Generalstabens litografiska Anstalt, 1946. 6 7 Plotted by O. Licstol, Oslo. Bases: J. B. Rekstad: Skoggnensens og sneliniens st0rrc h0itle tidligere i det sydlige Norge, Norges Geologiske Under so gelse, Aarbog for 1903, Vol. 36, No. 5; Knut Faegri: Ober die Langenvariationen einigcr Glctschcr dcs Jostedalsbre, Bergens Museums Arbok 1933, Naturviden- skapelig rekke, No. 7; idem: Quartargeologische Untersuchungen im westlichen Norwegen, I-II, Bergens Museums Arbok, Heft 3, No. 8, 1935, and Heft 2, No. 7, 1910; Erik Granlund: De svcnska hogmossarnas geologi, Sveriges Geol. Unders. Ser. C., No. 373, Arsbok, Vol. 26, No. i, 1932. 68 Jon Eythorsson: Tliykkt Vatnajokuls, Jokull, Joklarannsoknafelag Islands, Vol. i, Reykjavik, 1951. <*>> Sigurdur Thorarinsson: The Thousand Years' Struggle Against Ice and Fire (Special University Lecture, Bedford College, London University, February, 7<> H. W:son Ahlmann: The Present Climatic Fluctuation, op. cit., p. 166. P. N0rlund: De gamle Nordbobygder vcd Vcrdcns Ende, Copenhagen, 1934; J. Iverscn: Nordboernes Undergang paa Gr0nland i geologisk Belysning, Gron- landske Selskabs Aarsskrift, 1034-35, 1935. 71 P. N0ilund: Buried Norsemen at Herjolfsnes: An Archeological and Historical Study, Meddelelser om Gr0nland, Vol. 67, 1924, pp. 1-270 (see the abstract by William Hovgaard: The Norsemen in Greenland, Geogr. Rev., Vol. 15, 1925, pp. 605-616); Lauge Koch: The East Greenland Ice, Meddelelser om Gr0nland,Vo\. 130, 1915. 72 H. W:son Ahlmann: The Present Climatic Fluctuation, op. cit., p. 166 73 H. Kinzl: Die grossten nacheiszeitlichen Gletschervorstosse in den Schweizer Alpcn und in der Mont Blanc-Gruppc, Zeitschrift flir Gletscherkunde, Vol. 20, JOS 2 ' PP- 269-397. 74 F. E. Matthes: Glaciers, op. cit., p. 207. 75 Sigurdur Thorarinsson: Some Tephrochronological Contributions to the Volcanology and Glaciology of Iceland, Geografiska Annaler, Vol. 31, 1949, pp. 239-256. See also E. M. Todtmann: Im Gletscherruckzugsgebiet des Vatna Jokull auf Island, Neues Jahrb. Geol. und Palciontologie, Nov. 1951, Stuttgart, 95 l - 76 H. W:son Ahlmann: Glaciers in Jotunheim and their Physiography, Geografiska Annaler, Vol. 4, 1922, pp. 1-57. 77 Leo Aario: Ein nachwarmezeitlicher Gletschervorstosse in Oberfernau in den Stubaier Alpen, Acta Geographica, Vol. 9, No. 2, Helsinki, 1944, pp. 1-31.